Spark plug



Feb. 5, 1935. v ANTHONY 1,989,670

SPARK PLUG Filed July 17, 1931 FIG. I.

INVENTOR: FELIX M. ANTHONY ATTORNEY.

Patented Feb. 5, 1935 UNITED STATES PATENT OFFICE one-fourth to KennethC.

Gillis and one-fourth to Darrell B. Edwards, both of Oakland, Calif.Application July 17, 1931, Serial No. 551,334

1 Claim.

This invention relates to improvements in spark plugs and moreparticularly to the electrode terminals of spark plugs for internalcombustion motors.

The principal object of the invention is to provide a spark plug thatwill fire at high working pressures in the modern high speed, highcompression automobile motors, at every ignition cycle.

Another object .is to provide a spark of large volume discharged betweenterminals of considerable area to create a flame-like ignition for thepropagation of combustion in the firing chamber.

Other objects and advantages will appear as the description progresses.

In this specification and the accompanying drawing the invention isdisclosed in its preferred form. It is to be understood, however, thatit is not limited to this form because it may be embodied in other formswithin the purview of the claim following the description.

In the one sheet of drawings:

Fig. 1 is a vertical section of a spark plug constructed in accordancewith this invention.

Fig. 2 is an end view of the same from below.

Fig. 3 is a fragmentary detail side view in crosssection of a modifiedform of ground electrode.

Figs, 4 and 5 are horizontal section and plane viewsrespectively of thegrid firing surface of the electrodes.

In detail the construction illustrated in the drawing comprises theouter shell 1, having the threaded neck 2 for engaging the cylinder headof the motor, not shown. The shoulder 3 provides for compressing theusual gasket against the cylinder head when the shell is screwed thereinby means of the hexagonal portion 4.

The center bore of the top portion is internally threaded to receive thethreaded bushing 5, having the hexagonal head 6.

The dielectric core 7 is usually formed of porcelain, compressed mica orother refractory material. This core extends through the shell 1 and isheld in fixed position by screwing down the bushing 5 which forces thecore against a suitable shoulder provided within the shell 1.

The center electrode 8 extends entirely through the core and engages theconventional terminal 9 fixed in the end of the core. The inner end ofthe electrode is swaged to form the head 10, the plane of which istransverseto the axis of the electrode. The electrode projectssufiiciently to locate the head beyond the end of the core 7, and beyondthe end of the shell also. The mechanical characteristics of spark plugsvary with the type of motor in which they are used, which modificationsare applicable to the present invention by those skilled in the art,without departing from the spirit of the invention.

The ground terminal 11 is fixed in the edge of the shell in the usualmanner and bent at 12 to bring the end 13 in juxtaposition to the head10. The end 13 is flattened to form a plate in juxtaposition to the headwith its plane parallel with the plane of the head 10.

The opposed surfaces of the head and plate 13 are provided with amultiplicity of depressions 14 and 15 respectively, which form a pair ofgridlike surfaces 1617 on the whole areas of the op posed faces of saidhead 10 and plate 13. Both surfaces are preferably of substantially thesame area.

Much of the success of the present invention is ascribable to this gridsurface in combination with the parallel planes of these heads and theincreased areas of each. Before a spark can bridge the gap, the gaslying between must be ionized. With the conventional type of gap theseions are blown away with the incoming gas stream of the intake cycle,while in this invention, a large number of ions are retained in therecesses of the grid surface. As a consequence, less potential isnecessary, and a greater volume of current is permitted to flow acrossthe gap. As the heat increases with the increase of current flowing, amuch hotter spark is produced, which is necessary when typical blendedgasolines are used.

The value of the above mechanical combination becomes apparent whenviewed in connection with the operation of the ignition system. Theinstant the coils secondary system becomes active, a strong electricfield" is produced between and around the points of the plug and the airand gas lying in this field become ionized and the current in a spark iscarried across the gap by these ions or charged particles. These ionsare usually present in any gas. in very small numbers, and permit thepassage of an extremely small current only. This current is so smallthat ordinarily, air, or any other gas, can be considered as a perfectinsulator. But if these ions are present in an electric field betweentwo charged electrodes, they are affected by mechanical forces and willmove along the axis of the field. This movement necessarily producescollisions with other molecules, and when the ions have acquiredsufiicient momentum, the collision causes disruption of a neutralmolecule with the production of twonew electrically charged ions ofopposite sign. This action continues to carry on under the influence ofthe electric field, and collisions'with other molecules produce afurther supply of ions at an ever increasing rate, and when sumcientions become available, the energy of collision materializes as light andheat, and the current passesacross the gap as a spark. It follows,therefore, that any condition, such as the opposed grid surfaces, thatwill trap and retain' a considerable quantity of such ions willcontribute to the improved operation of the spark plug, especially underhigh pressure conditions.

Heretofore, it has been the practicerto merefiy arrange a gap betweenthe wire electrodes of the older types of internal combustion motors.

In the modern high compression, high speed motors with multiplecylinders, the ignition interval is so short and frequent that the sparkplug must be intenseiy responsive or the spark will be quenched by thehighly compressed fuel,

to and above 150 pounds pressure.

or the current will find a path of less resistance than the gap;

In actual t isual pressure tests the best spark plugs now available inthe open market will begin skipping at from 50 to 65 pounds pressure persquare inch and will fail entirely at '70 to '75 pounds. Under the sameconditions the Present spark plug continues to fire at pressures up Thedischarge between the grid surfaces of the head 10 and plate 13 isin thenature of a flaming zone that never fails to propagate a flame in thecompressed fuel, even when a weaker spark of the old type will jumpthrough the fuel without producing complete combustion, or fail to sparkat all.

It is desirable to keep the bend 12 below the level of the spark gap todrain accumulated oil away fromthe gap between the terminals.

The modifications shown Fig. 3 is only in the mechanical construction ofthe ground terminal. All corresponding parts are identified with thesame reference characters with the addition of X to indicate themodifications.

Having thus described this invention what is claimed and desired tosecure by Letters Patent is: l 1

A spark plug having insulated electrodes having confronting terminalsurfaces arranged in parallel juxtaposition and having inter-spaceddepressions therein so as to form a fiat grid-like lattice surface abovethe bottom of the depresslons.

Fnmx M. ANTHONY.

